30/07/2024
Folks with lame horses:
Many of you are perplexed why a horse is lame at the trot, but not at the walk or canter.
The trot is the "lameness gait". It is the simplest gait, with a two-beat stride pattern, and the horse's weight is distributed evenly between diagonal pairs of legs (the front left and hind right strike at the same time and vice versa). The trot is faster than the walk and puts more force on the foot or leg, making it easier to detect lameness. In the canter, a horse can hide a lame limb because it is a three-beat gait.
When trying to evaluate which limb is lame, the easiest is when it is a front limb. Remember this: "Head Down On Sound". So, the head will be down when the sound leg hits the ground. The head will be up when the lame limb hits the ground. Best way to see this is to watch the horse's head when it is trotting - move your head in beat with the horse's head, then look at the front limbs and see which one hits the ground when your (and the horse's) head is up.
Hind limbs can be tricky. Often the head will be UP when the sound limb hits the ground - remember the diagonal limbs hit the ground at the same time. The horse will try to unweight the hindlimb by putting the head down, pulling the back end up.
Sometimes you need to look at hip height while the horse is trotting away from you. Admittedly, hind limb lamenesses are sometimes tricky even for seasoned vets.
Do we stop there? No! There's an entire limb to narrow down!
Then we get into further diagnostics. Flexions and nerve blocks first - once the area is narrowed down - is it soft tissue (muscle, tendons, ligaments) or bone - do we need x-ray or ultrasound? Do we need MRI? Bone scan? Etc. NONE of these things can be done by us HVC veterinarians - it requires a hands-on exam.
A comprehensive lameness exam is a big puzzle and thank goodness there are vets around that like that kind of puzzle.
